Question

Clogged catalytic converter? Honda Civic EX

it gave me the codes:
P0340-which it the camshaft positioning sensor... (i already got that fixed)
P0420-thats an converter thats not working as efficiently as i should be.
My spark plugs are pretty burnt out, but would that really be whats wrong?

The fouled or burnt plugs contribute to the clogging of the cat. When you say burnt out are they white/ashy looking? How are the gaps?I'd go ahead and replace them and then after that look at replacing the cat. If you aren't sure about the cat, have a back pressure test done on it. But with the symptoms you've described I'd bet its the cat. But get it checked prior to replacing.

The fouled or burnt plugs contribute to the clogging of the cat. When you say burnt out are they white/ashy looking? How are the gaps?I'd go ahead and replace them and then after that look at replacing the cat. If you aren't sure about the cat, have a back pressure test done on it. But with the symptoms you've described I'd bet its the cat. But get it checked prior to replacing.